1. Field of Invention
This invention relates to an azimuth sector scan radar system and more particularly to a low cost, high resolution sector scan radar.
2. Description of the Prior Art
As is well known to the prior art, azimuth sector scan radars are used to search out and pinpoint targets within a narrow azimuth section (.+-.1.degree. from relative azimuth bearing). These radar systems are typically used aboard military type aircraft for locating targets on the ground and for obtaining information relating to the range and relative azimuth bearing of the target from the aircraft, and presenting this information in a cockpit video display where it may be used by the pilot to control and direct the aircraft weapon systems. These systems must necessarily provide a high degree of accuracy, and must also provide a high resolution video image for the information being displayed on the video monitor. In addition, its airborne use requires that consideration be given to minimize the system size and weight.
The requirements for the video display include a bright clear video image, which allows observation of the video display in an open cockpit without the requirement of a hood over the face of the CRT, and also a short period of retention of the video image on the screen to accommodate the high mobility of the aircraft and the instantaneous change of target with respect to the aircraft. To achieve this, prior art systems have incorporated the use of a television raster type display which allows the use of a cathode ray tube with a short persistent phosphor. One such method of providing radar information on a raster display is disclosed in a patent to Breeze U.S. Pat. No. 3,653,044, wherein radar information from an antenna which scans through an azimuth angle of 180.degree. within one and one-half seconds, and which transmits main bang synchronization signals at a frequency of approximately 810 Hz, is processed for presentation on a television raster which has a horizontal trace rate of 15.75 kHz and a vertical trace rate of 60 Hz. That system converts the low frequency radar video to the higher raster frequencies through the use of multiple scan converter stages which includes video storage and video mixer stages with synchronization between these stages provided by a multiple number of clock frequencies. This frequency conversion process requires the use of extensive and complex circuitry, in addition to a multiple number of precision timing bases, which has an adverse affect on system reliability in addition to system size and cost. That system, however, is representative of the state of the prior art with respect to providing the required video characteristics.
At the present time, the prior art methods of providing bright, high resolution, video displays of radar sector scan information through the use of low persistence cathode ray tubes have been limited to the use of such raster type presentations.